It has heretofore been suggested that in presses and the like, gas springs be utilized in lieu of metal springs for absorbing the loads encountered, for example in stamping. In such systems, a plurality of gas springs are connected by individual lines to a source of gas under pressure. It is desirable to be able to not only pressurize the cylinders to a common pressure but also replenish the gas that might be lost in use. In addition, it is desirable to be able to reduce the gas pressure in the cylinders. It has been suggested that complex charging and relief valves be provided in gas cylinders.
Among the objectives of the present invention are to provide a gas cylinder for use in a system having a plurality of such gas cylinders, each having a line extending to a pressurized source wherein gas pressure can be replenished or reduced, which is simple to construct, relatively low in cost, and can be easily maintained.
In accordance with the invention, a gas spring comprises a cylindrical body with a bore, a piston rod positioned in the body and having an end projecting beyond one end of the body, a base closing the other end of the body, the cylindrical body and piston rod interengaging one another to limit relative outward movement of the piston rod with respect to the body. The gas spring includes a radial inlet through the wall of the cylindrical body into the base. A one-way valve is positioned in the base within the inlet and an axial inlet pressure passage extends from the outlet end of the valve to the interior of the cylinder. A radial bore is provided in the base and communicates at one end through an axial pressure relief passage to the interior of the cylinder. A pressure relief shuttle piston is positioned in the radial bore and a radial passage extends from the end of the shuttle piston remote from the axial pressure relief passage to the radial inlet of the cylindrical body. A spring yieldingly urges the pressure relief piston toward the axial pressure relief passage.